The present invention relates to a taper micrometer, and more particularly to a taper micrometer capable of directly and accurately measuring the taper of a tapered surface.
It is known that the taper on the internal surface of a cone can only be measured indirectly and the measuring methods usually used are as follows:
(1) A sine bar of a sine plate is used and by the provision of various kinds of dial gauges one can read the taper.
(2) In mechanical manufacturing plant, a number of standard taper gauges are selected to match with the internal surface of the cone one by one to approximately estimate the taper.
It is well-known that the above two methods of measuring are costly and can not read the taper entirely accurately.
Recently, an American named Mr. George L. Gershman invented a taper micrometer capable of measuring the taper more easier and more accurately, and which is known as taper-mike, manufactured by the Taper Micrometer Corporation in America and widely used around the world.
As shown in FIGS. 1A and 1B, a taper-mike (shown in FIG. 1B) contrasts a sine bar measuring device (shown in FIG. 1A) in structure. As can be seen from FIGS. 1A and 1B, a micrometer head, which is capable of longitudinal translation, of the taper-mike replaces the gage block in the sine bar measuring device.
In FIG. 1C, there is shown a taper micrometer used for measuring the taper of the internal surface of a cone also manufactured by the Taper Micrometer Corporation in America. It can reasonably be pointed out that as to whether both measuring pieces C1, C2 are coplanar with the axis of the cone of which the taper of the internal surface is to be measured can only be conjectured by the condition of measuring pieces C1, C2 contacting the internal surface of the cone. Further, the value read from the taper micrometer is equivalent to the height of the gauge block in a sine bar measuring device and must be transformed through some calculations to obtain the taper. As can be referred to in FIG. 1D, the calculating formulas are as follows: EQU t=2a/c (the definition) (1) EQU h=4t*b/(4+t*t) (2) EQU t=2(b-root(b*b-h*h))/h (3) EQU .theta.=arc sin h/b (4) EQU t=2 tan .theta. (5)
where:
t: the taper PA1 c: the length of the cone being measured PA1 2a: the diameter difference of two circles passing two points on the cone being measured PA1 h: the height of the gauge block PA1 .theta.: the angle enclosed by the cone surface and the cone axis PA1 b: the length of the sine bar
Thus, the calculation for obtaining the taper of a cone is time-consuming.
Applicant has therefore attempted to obviate the above disadvantages encountered by the widely used taper micrometer and the prior art.